Generally, a real-time 3D ultrasound diagnostic system is a medical tool for providing clinical information, such as 3D information and anatomical profiles, which could not be provided by a conventional 2D image, in a real-time manner. This kind of medical tool now tends to be widely used for the purpose of internal or obstetric treatment. This 3D ultrasound diagnostic system scans and converts 3D data for a target object received from a probe, renders the 3D data, and displays the rendered 3D ultrasonic image on a display device, such as a monitor or a screen, to let the user observe the 3D ultrasonic image of the target object in a real-time manner.
FIG. 1 shows view 1 of the object displayed on a monitor after scanning, conversion, and rendering of 3D data. As shown in FIG. 1, view 1 consists of 3D ultrasonic image 2, 2D ultrasonic image 3 of a coronal view representing the front of 3D ultrasonic image 2, 2D ultrasonic image 4 of a sagittal view representing the side of 3D ultrasonic image 2, and 2D ultrasonic image 5 of a axial view representing the top side of 3D ultrasonic image 2. If a user moves one of ultrasonic images 2-5 of view 1, the rest of the images move together.
The user can obtain clinical information for a target object by operating view 1 displayed based on ultrasonic images 2-5 (i.e., placing view 1 in an operation state) or not operating (i.e., placing view 1 in a static state) any view. The operation state means a view operation, such as movement, upscale, downscale or rotation of ultrasonic images 2-5, or movement of a Region of Interest box (not shown). However, in an operation state, much time is consumed for performing the arc-tangent calculation to scan and convert 3D data forming ultrasonic images 2-5 to 3D rectangular coordinates. Furthermore, since the locations of the 3D data are changed by the conversion of the ultrasonic images, the amount of data to be processed increases.
With reference to FIG. 2, the relationship between the 3D data and view 1 displayed with ultrasonic images 2-5 is described. FIG. 2(a) illustrates 3D data for an object in 3D rectangular coordinate view, FIG. 2(b) illustrates 3D data, as shown in FIG. 2(a), in Y-Z rectangular coordinates, and FIG. 2(c) illustrates 3D data, as shown in FIG. 2(a), in X-R rectangular coordinates, wherein X, Y and Z axes constitute the 3D rectangular coordinates of the view, and the R axis crosses at a right angle with the X axis from the point where 3D untrasonic images start to be obtained.
3D data for an object, received from a mechanical scanning type probe moved by a mechanical arm or rotated by a stepping motor, reside in 3D spatial coordinates, e.g., in conical coordinates as shown in FIG. 2(a). Thus, the user can observe the displayed ultrasonic images by scanning and converting the 3D data in the conical coordinates, and by rendering the converted 3D data. These conical coordinatescan be obtained by calculating the following equations:
                    R        =                                                            y                2                            +                              z                2                                              -          a                                    Eq        .                                  ⁢                  (                      1            ⁢            a                    )                                                  β          =                                    π              2                        +                                          tan                                  -                  1                                            ⁡                              (                                  y                  z                                )                                                    ,                  σ          =                                    π              2                        +                                          tan                                  -                  1                                            ⁡                              (                                  y                  R                                )                                                    ,                  r          =                                                                      x                  2                                +                                  R                  2                                                      -            b                                              Eq        .                                  ⁢                  (                      1            ⁢            b                    )                    Wherein: β, which is in the range of 0-180 degrees, is a scan viewing angle in the range of a swing angle of the stepping motor in the probe; σ, which is in the range of 0-180 degrees, is a probe viewing angle in the range of a width angle of an 2D image scanned by the probe; r is the distance between the starting point of the 3D data and any 3D data in the ultrasonic image; a is the distance between the apexes of the scan viewing angle and the probe viewing angle; and b is the distance between the apex of the probe viewing angle and the starting point of the 3D data. Further, x, y and z are values on X, Y and Z axes, respectively.
In an operation state, in order to find precise conical coordinates of the 3D data to be re-displayed as a converted ultrasonic image by a view operation, calculating Eqs. (1a) and (1b) is unavoidable, which prevents the ultrasonic images converted by the view operation from being rendered in a real-time manner.
Further, in a static state where no view operation is involved, even though 3D ultrasonic images and 2D ultrasonic images therefrom can be rendered in a real-time manner, the processing speed of scanning and converting 3D data to a 3D rectangular coordinate view is relatively low.